Surgical needle coatings and methods

ABSTRACT

The present invention provides improved medical devices for use in surgical procedures and methods for manufacturing improved medical devices. In some embodiments, the improved medical devices can include improved surgical needles that are capable of being repeatedly passed through tissue using minimal force. More particularly, the improved surgical needles can be manufactured with two or more different coatings that provide the surgical needles with both durability and lubricity for ease of repeated and successive passes through tissue. Improved methods for manufacturing the surgical needles and for providing and applying coatings to the surgical needles are also provided.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 12/614,669, filed on Nov. 9, 2009 and entitled “Surgical NeedleCoatings and Methods,” which is hereby incorporated by reference in itsentireties.

FIELD OF THE INVENTION

The present invention relates to coated medical devices and methods formanufacturing the same.

BACKGROUND OF THE INVENTION

Coated medical devices which repeatedly come into contact with bodilytissue, such as surgical needles, are required to be lubricious, yetdurable enough to withstand multiple contacts with tissue. However,lubricity is often sacrificed at the expense of making a more durablecoating that adheres well to medical devices. There are many coatingmaterials that are extremely lubricious, but either do not adhere wellto the desired substrates or easily wear off the substrate during use.Likewise, many extremely durable coatings exist, but these coatings arenot considered lubricious. Various attempts have been made to findcoating compositions and/or a method of applying coating compositionsthat can provide durability and lubricity simultaneously. Accordingly,the present invention solves this problem by providing coatingcompositions and methods of application, which provide both durabilityand lubricity, as well as decreased manufacturing time.

SUMMARY OF THE INVENTION

While any medical device can be provided with regard to the examplesdescribed herein, in one exemplary embodiment, a surgical needle isprovided having an elongate body with a tissue-penetrating end and asuture attachment end. The surgical needle can have a base coatingdisposed on an exterior surface of the elongate body and a top coatingthat differs from the base coating. The top coating can include alubricious silicone disposed on the base coating such that the basecoating bonds with the top coating and enhances the durability of thetop coating.

In one embodiment, the surgical needle can be passed through tissue, anda force required to penetrate the tissue-penetrating end of the elongatebody through tissue can remain substantially constant after multiplepasses through tissue (e.g., at least about twenty times and morepreferably, at least about thirty times). The surgical needle can beformed from any suitable material known in the art including, but notlimited to, tungsten-rhenium alloys, refractory alloys, stainlesssteels, nitinol, and tantalum.

In some embodiments, a primer coating can be disposed between theexterior surface of the elongate body and the base coating and can bondwith the exterior surface of the elongate body and the base coating. Theprimer, base, and top coatings can be formed from any suitablecomposition known in the art, but in one exemplary embodiment, theprimer coating can be silicone-based, the base coating can include avinyl functionalized organopolysiloxane, and the top coating can includea hydroxyl terminated polydimethylsiloxane and a methyl-hydrogensiloxane.

In another embodiment, a surgical needle is provided and can include anelongate body formed from a tungsten-rhenium alloy and having atissue-penetrating tip. A primer coat can be disposed on an exteriorsurface of the elongate body and can covalently bond with reactivefunctional groups on the exterior surface of the elongate body. Anynumber of coatings can be disposed over the primer coat, for example, abase coat can be disposed over the primer coat and a top coat can bedisposed over the base coat. In some embodiments, the base coat can bondwith the primer coat, and the top coat can bond with the base coat.Bonding can include, for example, at least one or both of covalentbonding and cross-linking.

In other aspects, a surgical needle is provided and can include anelongate member having a tissue-penetrating tip and a suture attachmentportion. The elongate member can have, for example, base and topcoatings. The coatings can be formed from any suitable composition, butin one embodiment, the base coating can include a vinyl functionalizedorganopolysiloxane and a hydrofluoroether solvent, and the top coatingcan include a polydimethylsiloxane and a hydrofluoroether solvent

Various coating methods known in the art can be used to apply thecoatings, for example, the base and top coatings can be spray-coatedonto the elongate member. In some embodiments, the elongate member canfurther include a primer coating formed from a coating mixture that caninclude a silicone resin and a solvent. The elongate member can beformed of any suitable material known in the art including, but notlimited to, a tungsten-rhenium alloy. The primer coating can be disposedon and can at least partially covalently bond with the elongate member.The base coating can be disposed on the primer coating, and the topcoating can be disposed on the base coating. The coatings can have anythickness sufficiently effective for a particular application.

Methods for coating a surgical needle are also provided, and in oneembodiment, a method for coating a surgical needle can include providinga surgical needle having a tissue-penetrating end and a sutureattachment end, applying a base coating to a surface of the surgicalneedle, and applying a top coating that differs from the base coatingonto the base coating. The base coating can bond with the top coatingand can enhance the durability of the top coating.

Many curing and processing methods can be applied to the coatings and inone embodiment, after applying the base coating and prior to applyingthe top coating, the method can include curing the base coating. Inaddition, the method can further include, prior to applying a basecoating and applying a top coating, preparing the base coating from amixture that can include a vinyl functionalized organopolysiloxane and ahydrofluoroether solvent, and preparing the top coating from a mixturethat can include a polydimethylsiloxane and a hydrofluoroether solvent.

In some embodiments, prior to applying the base coating, the method caninclude applying a primer coating onto the surface of the surgicalneedle such that the base coating can be applied onto the primercoating. The surgical needle can be formed of any biocompatible materialknown in the art including, but not limited to, tungsten-rhenium alloys,refractory alloys, stainless steels, nitinol, and tantalum. In oneembodiment, the primer coating can at least partially covalently bondwith a surface of a needle made from a tungsten-rhenium alloy.

In other aspects, a method for coating a surgical needle can includeproviding a surgical needle having a tissue-penetrating end and a sutureattachment end, positioning the surgical needle between first and secondnozzles, the first and second nozzles being opposed to and facing oneanother, and activating the first and second nozzles to spray a basecoating onto a surface of the surgical needle. The method can furtherinclude positioning the surgical needle between third and fourthnozzles, the third and fourth nozzles being opposed to and facing oneanother, and activating the third and fourth nozzles to spray a topcoating on at least a portion of the base coating, the top coatingdiffering from the base coating.

In some embodiments, each nozzle can dispense a rotating spray ofcoating particles that swirl around the surgical needle to coat thesurgical needle. The method can further include adjusting an angle of afluted tip within each nozzle to control a pitch of the rotating spraydispensed by the nozzle and moving the surgical needle and the first andsecond nozzles relative to each other at a relative speed in the rangeof about 1 inches per second to about 15 inches per second, and morepreferably in the range of about 3 inches per second to about 15 inchesper second, while the nozzles are activated to spray a coating. Thefirst and second nozzles can be positioned at an angle less than 180°relative to one another in a horizontal plane. The base and top coatingscan have any thickness sufficient to effectively provide the desiredcharacteristics.

In other embodiments, a method for coating a surgical needle can includeproviding a surgical needle formed from a metal alloy, applying a primercoat to the surgical needle, the primer coat at least partiallycovalently bonding with the metal alloy, applying a base coat onto theprimer coat, the base coat bonding with the primer coat, and applying atop coat onto the base coat, the top coat bonding with the base coat.The base coat and the top coat can be applied by spray-coating. Thecoatings can have any suitable composition known in the art, forexample, the primer coat can include a silicone, the base coat caninclude a vinyl functionalized organopolysiloxane, and the top coat caninclude a methyl terminated polydimethylsiloxane.

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one exemplary embodiment of a surgicalneedle;

FIG. 2 is a side view of a carrier strip with surgical needles attachedthereto for transporting the surgical needles;

FIG. 3A is a perspective view of one exemplary embodiment of a swirlcoating machine for swirl coating surgical needles;

FIG. 3B is a perspective view of another exemplary embodiment of a swirlcoating machine for coating suspended surgical needles;

FIG. 4 is a flowchart of one exemplary method for manufacturing andcoating surgical needles;

FIG. 5 is a graphical representation comparing the force required topass primed and unprimed surgical needles through synthetic media;

FIG. 6 is graphical representation comparing the force required to passsurgical needles that are swirl coated through synthetic media versussurgical needles that are dip coated;

FIG. 7 is a graphical representation comparing forces associated withtwo different coating compositions and application methods;

FIG. 8 is a graphical representation comparing the force required topass surgical needles that are swirl coated through synthetic mediaversus surgical needles that are dip coated; and

FIG. 9 is a graphical representation comparing the forces associatedwith passing three different coating compositions and applicationmethods through human cadaver tissue.

DETAILED DESCRIPTION OF THE INVENTION

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those skilled in the art will understand that the devices andmethods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments and thatthe scope of the present invention is defined solely by the claims. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments. Suchmodifications and variations are intended to be included within thescope of the present invention.

The present invention generally provides improved medical devices foruse in surgical procedures and methods for manufacturing improvedmedical devices. In some embodiments, the improved medical devices caninclude improved surgical needles that are capable of being repeatedlypassed through tissue with ease of penetration. More particularly, theimproved surgical needles can be manufactured with two or more differentcoatings that provide the surgical needles with both durability andlubricity for ease of repeated and successive passes through tissue.Improved methods for manufacturing the surgical needles and forproviding and applying coatings to the surgical needles are alsoprovided.

While many types of medical devices and surgical needles arecontemplated, in one embodiment, a biocompatible surgical needle isprovided having two or more different coatings applied successivelythereto. A base coating can be applied to the needle to providedurability for a different top coating that is applied to providelubrication. The base coating can also be lubricious to enhance thelubricity of the top coating. In some embodiments, the base and topcoatings interact, for example, by cross-linking or other bondingmechanism, so that the base coating retains the top coating on thesurgical needle. In this way, the base coating can assist in preventingthe top coating from wearing and/or rubbing off after repeated passesthrough tissue. In other embodiments, each of the base coating and/orthe top coating can cross-link with itself. The interaction between thedurable base coating and the lubricious top coating assists inmaintaining lubrication of the surgical needle so that it canconsistently and repeatedly be passed through tissue with minimal forcerequired.

Any number of coatings can be applied to the surgical needle dependingon the surgical application and the composition of the surgical needle.For example, in another embodiment a primer coating can be applied tothe surgical needle before the base and top coatings are applied. Theprimer coating can be different from the base and top coatings and itcan bond with a surface of the surgical needle to provide an appropriateand secure surface on which to apply the base coating. In turn, the basecoating can bond to the primer coating such that the primer coatingsecurely retains the base coating on the surgical needle.

Improved methods for applying the coatings to various medical devices,such as surgical needles, are also provided. In some embodiments, asurgical needle can be spray coated with one or more coatings to providethe surgical needle with a uniform distribution thereof. For example, aspray coating machine having two spray nozzles directed toward oneanother can be provided for successively applying each coating. One ormore surgical needles can be passed between the two spray nozzles asthey are spraying a coating. Such a configuration allows for uniformdistribution of the coating on the surgical needle and minimizes therisk of pooling and/or dripping of the coating. Multiple coatings can beapplied using this method, and prior to and/or after application of eachcoating, the surgical needle can be cured for a sufficient period oftime effective to set and bond the coating(s). As will be discussed inmore detail below, novel combinations of solvents and coating materialscan allow for substantially reduced cure times when compared withtechniques known in the art.

Exemplary surgical needles of the type contemplated herein can generallybe used for any surgical procedures now known or yet to be developed.The surgical needles can be capable of penetrating and passing throughany type of tissue, including any type of mammalian tissue includingsoft and hard tissues and tissues that have been calcified, and can beused to apply sutures to close an incision or wound, pass suture orother material through tissue, and/or simply create an opening intissue. A person skilled in the art will appreciate the variety of usesfor the surgical needles described herein.

Exemplary surgical needles can generally include an elongate member witha tissue penetrating tip on a distal end thereof for penetrating throughtissue. The tissue penetrating tip can be pointed and can be as sharp oras dull as required for a particular surgical procedure. In someembodiments, the surgical needle can also include a suture attachmentportion disposed on a proximal end of the elongate member for receivingand retaining suture. The surgical needle can have any geometry known inthe art, including straight, taper point, taper cut, cutting edge,bayonet-shaped, curved, circular, etc. In addition, the surgical needlecan have any cross-section including, but not limited to, round body,rectangular body, square body, ovular body, and I-beam. A person skilledin the art will appreciate the various combinations of shapes andcross-sections possible for a given needle.

In the manufacturing process, surgical needles can have a straightenedand/or hook-shaped grasping portion to assist in applying coatingsthereto. A conveyer mechanism and/or carrier strip for manufacturing aneedle and/or moving a needle through a coating machine and/or curingmechanism can retain the needle for manufacturing, coating, and curingby attaching to the grasping portion. An exemplary carrier strip 20 foruse with surgical needles 24 is illustrated in FIG. 2. The carrier strip20 includes various latches 22 for retaining the curved surgical needles24 thereon. This allows the surgical needles 24 to be moved using aconveyor style mechanism during the coating and/or curing process.

One exemplary embodiment of a surgical needle is illustrated in FIG. 1.As shown, a surgical needle 10 is provided having a curved elongate body16 with a tissue penetrating tip 12 formed on a distal end thereof. Thetip 12 has a circular cross-section and terminates in a sharp point forpenetrating tissue. The curved elongate body 16 extends between the tip12 and a suture attachment portion (not shown) and is in the form of anarc with a flattened, rectangular cross-section. While the surgicalneedle 10 can have any relative dimensions as needed, in the illustratedembodiment, a width W of the needle 10 is on the order of a height H ofthe needle 10. A suture attachment portion can have any form as neededfor receiving and retaining suture.

Exemplary surgical needles can be formed of any suitable, biocompatiblematerial known in the art. In some embodiments, a surgical needle can bemade of a metallic alloy, including, but not limited to, titanium,stainless steels such as 420 stainless steel, 455 stainless steel,ETHALLOY® Needle Alloy, and 302 stainless steel, refractory alloys,nitinol, tantalum, as well as various other materials and alloys knownin the art. In other embodiments, surgical needles can be made from atungsten-rhenium alloy. Use of tungsten-rhenium alloy in making surgicalneedles can give the needles greater stiffness, strength, and ductilitythan the use of some other materials. Increased stiffness and strengthproperties allow the needle to be resistant to elastic deformation andto thus resist bending and springing when pushed through tough tissue,for example, calcified tissue. Increased ductility prevents the needlefrom breaking when bent or curved by a surgeon. Any of the needle alloycompositions can contain some percentage of any one or more of nickel,cobalt, chromium, molybdenum, tungsten, rhenium, niobium, etc. Exemplaryneedles and methods for manufacturing needles and carrier strips can befound in U.S. Pat. No. 6,018,860, entitled “Process for ManufacturingDrilled Taper Point Surgical Needles,” which is hereby incorporated byreference in its entirety.

In general, two or more different coatings can be used to provideexemplary surgical needles with a durable lubricious surface forrepeated passes through tissue. In one exemplary embodiment, a base coatcan be used to coat an external surface of a surgical needle to providedurability to a top coat that is applied onto the base coat and thatprovides lubrication. The base coat preferably bonds with the top coatand thus prevents and/or lessens wear associated with repeatedpenetrations and passes through tissue. In some embodiments, a primercoat can optionally be applied prior to the base coat. The primer coatcan bond with the surface of the surgical needle to provide a bondingsurface for the base coat. The primer coat can add additional durabilityagainst wear for the base coat and top coat.

In some embodiments, the base coat can include a silicone basedcomposition characterized as a vinyl functionalized organopolysiloxane.The base coat solution includes a vinyl functionalizedorganopolysiloxane, polymethylhydrogen siloxane fluid cross-linkingagent, and optionally a catalyst such as a conventional metal catalystsuch as platinum or tin. The organopolysiloxane base polymer can be, forexample, Momentive® Product Code No. MSC2631 silicone manufactured byMomentive® Performance Materials of Waterford, N.Y. Further informationon the MSC2631 composition is available from the manufacturer's MSDS.

The base coat can be prepared using a solvent, for example, ahydrofluoroether (“HFE”) (e.g., HFE 72-DE solvent manufactured by 3M® ofSt. Paul, Minn.). The HFE solvent acts as a carrier for the siliconecomposition. It evaporates quickly from a composition under ambientconditions to limit migration of other substances in the composition andthus drastically reduces cure time of the composition. In addition, theHFE solvent leaves no residue after evaporation. It complies with healthand safety regulations and is environmentally friendly. As will beappreciated by those skilled in the art, any suitable solvent can beused including, but not limited to, HFE, xylene, heptane, IsoPar K (DowCorning), napthalene, toluene, and hydrofluorocarbons.

Additionally, a catalyst and a cross-linker can be added to the basecoat. For example, Momentive® Product Code No. SS8010 platinum catalyst(“catalyst”) and Momentive® Product Code No. SS4300 cross-linker(“cross-linker”), both manufactured by Momentive® Performance Materialsof Waterford, N.Y., can be added during the preparation of the base coatto act as a cross-linker and catalyst. As will be appreciated by thoseskilled in the art, any suitable catalysts and cross-linkers can be usedincluding, but not limited to, other cross-linkers containing asilicon-hydrogen moiety. Other catalysts may include conventional metalcatalysts such as tin.

In preparing an exemplary base coat, 27.57 wt. % of the base siliconepolymer, for example, a vinyl-functionalized organopolysiloxane, can becombined with 72.27 wt. % of the HFE solvent and mixed and/or agitatedfor an appropriate period of time, for example, for about five minutes.The catalyst can then be added to the mixture at 0.02 wt. % and thecross-linker can be added at 0.14 wt. %. The mixture can be agitated foranother few minutes to ensure homogeneity, for example, about one to twomore minutes. For an exemplary 48.43 g base coat sample, 13.35 g of thebase silicone polymer can be combined with 35.00 g of the HFE solvent,0.012 g of the catalyst, and 0.068 g of the cross-linker.

A top coat can be applied to a surgical needle. In some embodiments, thetop coat can include a silicone based composition characterized as ahydroxyl terminated polydimethylsiloxane. The hydroxyl terminatedpolydimethylsiloxane generally includes dimethyl siloxane-hydroxyterminated, methylhydrogen siloxane, and trace amounts of several othersiloxanes. The hydroxyl terminated polydimethylsiloxane can be, forexample, NuSil® Technologies Silicone Product No. MED4162 manufacturedby NuSil® Technologies of Carpentaria, Calif., which is a dispersionthat contains 30% solids silicone in a 70% xylene solvent carrier.

The top coat can be prepared using a solvent, for example, the HFEsolvent or any other compatible volatile-solvent. In preparing anexemplary top coat, 26 wt. % of the top silicone polymer can be combinedwith 74 wt. % of the HFE solvent. For example, for a 50 g top coatsample, 13.00 g of the top silicone polymer can be combined with 37.00 gof the HFE solvent.

In some embodiments, a primer coat can optionally be applied to asurgical device prior to applying the base coat. The primer coat canhave any formulation capable of bonding to a surgical needle and capableof providing an appropriate substrate for applying a base coat. In oneembodiment, the primer coat can be formed of, for example,polyalkylsiloxane and tetraethyl silicate. A polyalkylsiloxane andtetraethyl silicate primer coat can be formulated for coatingdifficult-to-bond substrates such as, for example, tungsten-rheniumalloys.

One example of a polyalkylsiloxane and tetraethyl silicate primer coatis Momentive® Product No. SS4044P (“SS4044P primer”) manufactured byMomentive® Performance Materials of Waterford, N.Y. The SS4044P primercan include Momentive®) 10-30 wt. % of acetone, 1-5 wt. % of butanol,10-30 wt. % of xylene isomers mixture, 5-10 wt. % of ethylbenzene, 10-30wt. % of 2-propanol, 1-5 wt. % of tetraethyl silicate, and 10-30 wt. %of polyalkylsiloxane. Further information on the SS4044P primercomposition is available from the manufacturer's MSDS.

In general, as noted above, the primer coat can covalently bond to thesurgical needle to provide a substrate on which to apply other coatings.The base coat can be applied on top of the primer coat. As the top coatis applied over the base coat, the base coat will bond with the top coatto provide durability to the top coat. In essence, the bonding betweenthe primer coat and the surgical needle anchors the other two coats tothe needle surface. The bonding of the base coat to both the primer coatand the top coat anchors the top coat to the primer coat, and thus tothe surgical needle surface, giving the top coat extended durability.

The coatings can generally be applied at any thickness as needed. Thethickness of the individual coatings and the combined coatings should besufficient to provide the desired characteristics. For example, theprimer coat can be applied to have a thickness in the range of about0.01 μm to about 1 μm. The base coat and the top coat can be appliedwith a thickness in the range of about 1 μm to about 7 μm. In anexemplary embodiment, the top coat can have a thickness that is at leastabout 50% less than a thickness of the base coat. A person skilled inthe art will appreciate that the thicknesses of the coatings can varydepending on a particular application.

There are many methods and systems contemplated herein that can be usedto provide coated surgical needles or other medical devices. In general,a medical device such as a surgical needle can be produced from adesired material and prepared for coating, as described in more detailbelow. One or more coatings can be applied to the surgical needle toprovide durability and lubricity during use. Before, during, and/orafter application of any one of the coatings, the surgical needle can becured for a sufficient amount of time effective to remove solvents inthe coatings and/or to set, cross-link, and/or bond a coating.

Any process known in the art can be used to coat various medical deviceswith one or more of a base coat, top coat, and/or primer coat including,but not limited to, dipping, spraying, wiping, brushing, totalimmersion, gravity feed, etc. For example, surgical needles can be dipcoated in a number of traditional ways. If needles are being processedmanually, the needles can be hand dipped or totally submersed in acoating. In a more automated process, coating solutions can be appliedusing a weir type circulating system in which surgical needles passthrough the solution in an automatic fashion, either by robot orhandling system. Dip techniques generally rely on surface tension foradhesion of the coating and wetting characteristics of the coating withrelation to the substrate for continuity.

In one embodiment, one or more coatings can be applied to a surgicalneedle by spraying using, for example, ultrasonic and/or gas conformalcoating spray nozzle systems and/or swirl coating systems. Ultrasonicand gas spray nozzles transmit energy to a liquid in an amountsufficient to atomize the liquid and form a spray of droplets. The sprayof droplets can be applied to a medical device using a swirl process inwhich the droplets are swirled around the medical device in order tocoat the substrate. Application of a coating using the swirl process canensure a more even distribution of the coating to a surgical devicewhile preventing excess collection of the coating that may result indrips, undesired pooling, droplets, and/or unevenness. Spraying alsoallows for precise control and adjustment of coating thickness. Aparticular coating can be applied to leave only a thin film on a surfaceor it can be applied to provide different thicknesses.

Different types and sizes of spray nozzles can be used depending on thespecific coating compositions and the desired attributes of the spraystream generated. Spray nozzles can be designed to operate at specificfrequencies and/or air pressures as needed and the desired power levelfor operating the nozzles can depend on various factors including thesize and design of the nozzle, the viscosity of the composition beingused, the volatility of components in the composition being used, etc.Both ultrasonic and fluid spray nozzles are available commercially.

In one embodiment, such as those illustrated in FIGS. 3A and 3B, opposedspray nozzles 30 a, 30 b are provided for applying a swirl coating toexemplary surgical needles 32. The opposed spray nozzles 30 a, 30 b caneach be coupled to canisters holding a particular coating to be appliedand can deliver the coating through discharge openings 31 a, 31 b. Eachcoating to be applied by the swirl process can be applied usingdifferent pairs of opposed spray nozzles 30 a, 30 b. Thus, in someembodiments, multiple sets of spray nozzles can be used to applymultiple coatings. Each spray nozzle 30 a, 30 b can have a fluted tip(not shown) for delivering the coating. An angle of the fluted tip,relative to a horizontal plane through which the needles extendperpendicular to, can be adjusted to focus the band of spray to optimizecoating. As will be appreciated in the art, any angle can be used asneeded to deliver a particular coating. In addition, different coatingsmay require delivery from a fluted tip with a different angle.

The opposed pair of spray nozzles 30 a, 30 b can extend from apositioner (not shown) capable of adjusting and maneuvering the spraynozzles 30 a, 30 b in three dimensions. The opposed spray nozzles 30 a,30 b can be positioned in any way relative to each other as needed for aparticular application and can generally be symmetrically opposed to oneanother. In the illustrated embodiment, the spray nozzles 30 a, 30 b arepositioned at approximately a 30 degree angle, as shown in FIGS. 3A-3B,relative to a horizontal surface. Horizontally, the nozzles 30 a, 30 bcan be directly opposed, e.g., offset by 180 degrees. Preferably,however, the nozzles 30 a, 30 b can be horizontally offset relative toeach other by an amount less than 180 degrees to prevent neutralizationand to prevent overspray from collecting on the needles. The positioningof the opposed nozzles 30 a, 30 b can be optimized to provide the mostcomplete coating of a surgical needle.

In general, the swirl coating can be applied during relative movementbetween the needles 32 and the nozzles 30 a, 30 b. In some embodiments,one or more needles 32 can remain stationary while the nozzles 30 a, 30b move relative to the needles 32 while spraying the coating. In otherembodiments, a carrier strip, such as the carrier strip 20 shown in FIG.2, or a carrier strip 40 shown in FIGS. 3A and 3B, can move a pluralityof surgical needles 32 relative to the opposed spray nozzles 30 a, 30 bwhile the nozzles 30 a, 30 b remain stationary. In other embodiments,both the carrier strip 40 and the nozzles 30 a, 30 b can move relativeto one another. The carrier strip 40 can be mounted below the nozzles 30a, 30 b as shown in FIG. 3A, or the carrier strip 40 can be mountedabove the nozzles 30 a, 30 b as shown in FIG. 3B.

The movement speed of the carrier strip 40 and/or the nozzles 30 a, 30 bcan be controlled so that the spray nozzles 30 a, 30 b provide optimalcoverage and coating of the needles 32. For example, relative movementspeed between the needles 32 and the nozzles 30 a, 30 b can be in therange of about 1 to about 15 inches per second. Optimally, the relativemovement speed can be in the range of about 3 inches per second to about5 inches per second. Shields may be optionally disposed between thenozzle discharge openings 31 a, 31 b and the proximal portion of theneedle.

There are many mechanisms known in the art for curing, hardening, and/orsetting a coating on a surgical device such a surgical needle. Curingcan also cause evaporation of any solvent used in making the coating.Curing can generally be accomplished through exposure of a coatedsurgical needle to some form of temperature increase and/or humiditychange for a predetermined period of time. For example, the coatedneedles can be placed in a furnace or oven, a hotbox, a humidificationchamber, and/or an infrared chamber, among other forms known in the art.Curing times can range from “flash” curing of only a few seconds totimes longer than twenty-four hours.

During the curing process, the temperature and/or humidity can bemaintained at a single value for the entire time and/or it can beincreased or decreased as needed over time. Temperature can be monitoredand adjusted using, for example, a thermocouple and a potentiometer tocontrol power to heating elements. The potentiometer can bepreconfigured so that temperature measurements made by the thermocoupleat periodic increments along a length of the heating system aremaintained at or between a specified temperature range. In otherembodiments, temperature can be controlled using a feedback loop wheretemperature measurements that correlate to temperatures where surgicalneedles will pass are fed back to a power supply that continuouslyadjusts power delivered to the heated filaments to maintain a desiredtemperature range. A humidity monitor can be used to monitor and adjusthumidity. In some embodiments, each coating can be cured afterapplication thereof to the surgical needle. In other embodiments, allcoatings can be applied before initiating the curing process.

In one embodiment, an infrared emitter can be used to effect curing of acoating. Infrared emitters are available commercially from Heraeus®Noblelight, for example, Model SKL200-800. The actual emitters caninclude, for example, eight foot long thin heated filaments embeddedwithin a reflective channel used to focus and contain the heat. Theinfrared heating system can be oriented so that the channel's opening isfacing down. Surgical needles to be cured in the infrared heating systemcan be held vertically and passed between two concave reflective wallsof the channel at about, for example, ¼ inch from the heated filaments.Needles can be held on a carrier strip as they traverse the channel at aspeed in the range of about 3 inches per second to about 5 inches persecond, although any speed can be used.

While many methods for providing durable lubricious coatings on surgicalneedles are contemplated, a flow chart of an embodiment of oneparticular method is illustrated in FIG. 4. As shown, the method cangenerally include manufacturing the surgical needles, preparing thesurface of the needles for receiving a coating, coating the needles witha primer coat, base coat, and/or top coat, and curing the coatings. Aperson skilled in the art will appreciate the variations and additionsthat can be included in such a method.

In manufacturing the surgical needles, raw wire of a suitablecomposition can be unspooled and cut into blanks for shaping. While anysize blanks can be used depending on the size of the needle desired, inone embodiment, the wire can be cut into two inch blanks. Once cut, theblanks can be attached to a metal carrier strip, such as thatillustrated in FIG. 2. The blanks can be secured and shaped into theirpreferred needle form by any methods known in the art, includingforming, grinding, curving, etc.

Needles that are appropriately shaped can be cleaned to removecontaminates and to prepare the surface for receiving a coating. Forexample, the needles can be exposed to high pressure nozzles thatrelease water at high temperature and pressure. In other embodiments,the needles can be baked to high temperatures to release anycontaminates. Once the needles have been cleaned, they can beelectropolished for any amount of time necessary. The needles can beimmersed in the electropolish bath (e.g., sodium hydroxide, phosphoricacid, etc.) and subjected to direct current to remove ions at acontrolled rate. Once complete, the needles can be rinsed successivetimes, for example, two times, in de-ionized water baths.

In some embodiments, a primer coat, such as the SS4044P primer describedabove, can be applied to the newly manufactured and cleaned surgicalneedles. The primer coating can be used, for example, when the needle isa tungsten-rhenium alloy. The primer can be applied using any methodknown in the art including dipping or spraying, but in one embodiment,the primer is applied to the surgical needles by dipping. Using agrasper or carrier strip, the needles can be dipped into the primer atroom temperature for one to two seconds to effect complete coveragethereof. A person skilled in the art will appreciate that primers can beapplied at any temperature and for any length of time as appropriate fora particular primer. Reactive functional groups in the primer can reactwith the functional hydroxide groups in the surface of the surgicalneedles and covalently bond thereto. In some embodiments, after theprimer coating has been applied, the surgical needle can be flash curedfor about 20 seconds at an appropriate temperature, for example, about200 degrees Celsius. Once cured, the primer can create a boundarybetween the surface of the surgical needle and any later appliedcoatings.

A base coat, such as the Momentive® base coat described above, can beapplied to the external surface of the surgical needle, and over aprimer if utilized, for example, the SS4044P primer. Any applicationmethod known in the art can be used, but in one embodiment, the surgicalneedle is sprayed or swirl coated with the base coat using opposed spraynozzles. For example, the surgical needle can be passed between firstand second opposed spray nozzles to be coated. Application of the basecoat using the spray or swirl coating ensures an evenly distributedlayer of the base coat on the needle or over the primer, if utilized. Asthe base coat is applied, the solvent, for example, the HFE solvent, canrapidly evaporate to leave a thin layer of evenly distributed siliconeon the needle surface. In some embodiments, the base coat can be curedonto the surface by exposure to an “in-line” infrared heating system.The base coat can be exposed to a number of different wavelengths ofinfrared light and cured.

The coated medical device of the invention may also have a top coatapplied over the base coat, more preferably after the base coat ispartially cured. For example, the NuSil® top coat described above can beapplied over the Momentive® base coat. Any application method known inthe art can be used, but in one embodiment, the surgical needle can besprayed or swirl coated with the top coat using opposed spray nozzles.For example, the surgical needle can be passed between third and fourthopposed spray nozzles to be coated. Application of the top coat usingthe spraying or swirl coating technique ensures an evenly distributedlayer of the top coat over the base coat. As the top coat is applied,the solvent, for example, the HFE solvent, can rapidly evaporate toleave a thin layer of evenly distributed top coat over the base coat. Insome embodiments, after application of the top coat, the top coat can beflashed cured to drive off any excess solvent. The needles can be passedthrough, for example, a hot box or other heated curing system, for anytime and at any temperature necessary to accomplish evaporation of thesolvent. In one embodiment, the top coat can be flashed cured in aninfrared heater for approximately 20 seconds at a temperature in therange of about 165 degrees Celsius to about 200 degrees Celsius.

Following application of the top coat, the surgical needles can beoptionally re-spooled. In some embodiments, the coated surgical needlescan be exposed to a final curing process. For example, the re-spooledneedles can be placed inside a convection oven and cured at atemperature and time sufficient to further cure the coating. In oneembodiment, the surgical needles can be cured in the convection oven forapproximately four hours at about 165 degrees Celsius. In otherembodiments, the final cure can be performed at a temperature of about80 degrees Celsius for approximately three hours.

The cure times for the exemplary coatings and methods described hereinare extremely beneficial in that they are significantly less than curetimes for previous coatings and methods known in the art. Previouscoatings and methods could require curing of the surgical needles for upto 72 hours plus processing and coating time. The currently describedexemplary coatings and methods can reduced the total curing time to lessthan about 4 hours and possibly less than about 15 minutes, providing asignificant increase in efficiency for manufacturing of the needles.

The use of two coatings as described above results in surgical needlesthat exhibit reduced and/or generally constant tissue penetration forcecompared with standard surgical needles after an equivalent number ofpasses through tissue. Thus, both the lubricity of the needle as well asthe durability of the coating is improved. This effect is believed toresult for a number of reasons. For example, application of the base andtop coats using a swirl coating process provides an even distribution ofthe coatings over the substrate. This is most clearly represented inFIG. 6, which will be described in more detail below. In addition, thecompositions of the coatings in combination with the methods ofapplication and curing can result in significantly decreased averageforce required to repeatedly pass the needle through synthetic media, asshown in FIG. 7, which will also be described in more detail below.

The use of the optional primer coating can also be advantageous. Aprimer coating can be capable of chemically bonding to the needlesurface to provide a bonding substrate for the lubricious siliconecoatings to adhere to, resulting in increased durability of the base andtop coatings. For example, FIG. 5 illustrates the force required to passa needle through synthetic media in relation to the number of passesthrough synthetic media. As shown, needles without primer have a drasticrise in the force required after thirty passes when compared with primedneedles of identical material and configuration, which tend to maintaina fairly constant force up to at least thirty passes through syntheticmedia. More detail will be presented in the examples described below.

Coating performance for medical devices can generally be tested with avariety of conventional tests. In the case of surgical needles, coatingperformance and integrity is evaluated using a penetration test device.A portion of a coated surgical needle is held using a holding device,and the coated needle is then partially passed through a synthetic ornatural penetratable material some number of times. The material istypically a type of polymer or synthetic leather, for example, Permair,Rubber-Cal, Monmouth rubber, Porvair, etc. The needle can be passedthrough the penetratable material for about one to about twenty times,between about one to about twenty-five times, and most preferablybetween about one to about thirty times. The needle is then retractedfrom the media. The maximum force is recorded for each pass and is usedas a measure of the coating performance. Various attributes of coatingperformance can be tested using these techniques.

EXAMPLES

The following experiments were conducted to examine the effects ofvarying the needle coating materials and methods. For each test, theneedles were passed through Monmouth Duraflex MR40 NBR rubber membrane(“Monmouth rubber”), which serves to simulate flesh, or human cadavertissue. In the following non-limiting examples, from 4 to 10 needleswere used and individually passed through the penetration membranethirty times each. The maximum force in grams was recorded for each passand used as a measure of coating performance.

The surgical needles were mounted in a rotating stage to fix the needlein a position perpendicular to the penetration membrane surface andoriented on its radial profile with the axis of rotation on the sameplane as the plane of the penetration membrane. The needle was rotatedinto the penetration membrane, which was mounted on top of the loadcell. The maximum amount of vertical force was recorded as the needlewas pushed through the penetration membrane.

The following non-limiting examples serve to further illustrate theapplication:

Example 1

The following tests were performed to examine the effect coating methodshave on the force required to pass a needle through Monmouth rubbersynthetic media. The performance of needles that were dip coated wascompared with the performance of needles that were spray/swirl coated.

Test A

In Test A, five needles were prepared for penetration testing. Theneedles were made from ETHALLOY® Alloy stainless steel and had adiameter of 0.0105 inches. A base coating composition was prepared froma mixture of 20 wt. % of Micropro 600 and Micromatte 2000, produced byMicropowders Inc., mixed with 80 wt. % of HFE-72DE solvent. The MicroProand Micromatte powder weight ratio was at 4:1. Five test needles wereeach dipped into the base coating to coat their surfaces. The needleswere coated by hand via the dipping process and placed on a magnetictray. The tray includes raised magnetic strips for holding the proximalends of the needles secure during the curing cycle and transport whilethe distal end (tip) of the needles hang over the edge of the magneticstrips. This configuration prevents the needle tips from making contactwith the tray. The coated needles were then heated to 190 degreesCelsius in a convection oven for ninety minutes at ambient atmosphere.The needles were then allowed to cool at ambient temperature outside ofthe oven.

A top coating composition was prepared using 26 wt. % of NuSil® MED4162with 74 wt. % HFE-72DE solvent. The five needles were then each handdipped into the top coating composition. The needles were then heated to220 degrees Celsius in a convection oven and cured for four hours atambient atmosphere. The needles were allowed to cool at ambienttemperature outside of the oven.

Once cured, the five needles were each passed through the penetrationmembrane thirty times and the penetration force in grams was recorded asshown in Table 1 below.

TABLE 1 Pass ---> Penetration [g] Experiment Needle 1 2 3 4 5 6 7 8 9 1011 12 13 14 15 A 1 39 38 41 40 42 47 42 46 43 47 47 46 48 49 52 2 40 4245 46 46 49 50 55 51 51 56 53 56 57 63 3 40 41 41 47 45 46 49 51 51 4550 52 52 57 54 4 34 34 36 36 36 36 38 37 40 39 42 41 44 43 45 5 38 38 3840 42 44 47 45 48 48 46 50 49 52 51 St Dev 2.5 3.1 3.4 4.6 3.9 5.0 5.16.8 4.9 4.5 5.2 4.9 4.5 5.9 6.5 Avg 38.2 38.6 40.2 41.8 42.2 44.4 45.246.8 46.6 46.0 48.2 48.4 49.8 51.6 53.0 Pass ---> Penetration [g]Experiment Needle 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 A 1 53 4553 57 48 56 53 55 56 54 57 57 57 60 61 2 59 54 64 62 65 69 62 66 68 6871 75 73 72 69 3 56 55 58 56 57 60 61 59 62 61 61 62 60 64 62 4 45 45 4648 49 48 49 51 53 53 50 53 52 56 53 5 51 51 52 50 54 51 56 52 57 59 5358 61 58 58 St Dev 5.3 4.8 6.8 5.6 6.9 8.2 5.4 6.1 5.9 6.0 8.2 8.5 7.86.3 5.9 Avg 52.8 50.0 54.6 54.6 54.6 56.8 56.2 56.6 59.2 59.0 58.4 61.060.6 62.0 60.6

Test B

In Test B, five needles were prepared for penetration testing. Theneedles were made from ETHALLOY® Alloy stainless steel and had adiameter of 0.0105 inches. A base coating composition was prepared froma mixture of 20 wt. % of Micropro 600 and Micromatte 2000, produced byMicropowders Inc., mixed with 80 wt. % of HFE-72DE solvent. The MicroProand Micromatte powder weight ratio was at 4:1. The five test needleswere swirl coated with the base coating composition using a single passspray using the SC-300 Swirl Coat™ Applicator and the Century® C-341Conformal Coating System available from Asymtek® of Carlsbad, Calif.with the following parameters: 2 PSI fluid pressure, 50 PSI air assist,and 10 in/sec line speed. The coated needles were then heated to 190degrees Celsius in a convection oven and cured for ninety minutes atambient atmosphere. The needles were allowed to cool at ambienttemperature outside of the oven.

A top coating composition was prepared using 26 wt. % of NuSil® MED4162with 74 wt. % HFE-72DE solvent. The five test needles were swirl coatedwith the top coating composition using a single pass spray with thefollowing parameters: 10 PSI fluid pressure, 50 PSI air assist, and 5in/sec line speed. The needles were then cured for four hours at 220degrees Celsius. Once cured, the five needles were each passed throughthe penetration membrane thirty times and the penetration force in gramswas recorded as shown in Table 2 below.

TABLE 2 Pass ---> Penetration [g] Experiment Needle 1 2 3 4 5 6 7 8 9 1011 12 13 14 15 B 1 30 29 30 31 31 31 33 33 31 32 34 34 34 35 36 2 33 3231 35 33 34 34 35 34 35 35 36 36 35 37 3 29 28 30 29 30 30 31 31 32 3232 33 34 32 32 4 29 29 29 28 29 30 31 30 32 33 33 33 35 35 34 5 32 31 3333 32 32 35 34 34 33 34 35 36 35 36 St Dev 1.8 1.6 1.5 2.9 1.6 1.7 1.82.1 1.3 1.2 1.1 1.3 1.0 1.3 2.0 Avg 30.6 29.8 30.6 31.2 31.0 31.4 32.832.6 32.6 33.0 33.6 34.2 35.0 34.4 35.0 Pass ---> Penetration [g]Experiment Needle 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 B 1 34 3837 36 37 38 37 38 37 40 40 39 37 39 42 2 37 37 39 38 38 37 38 39 38 3940 39 40 40 41 3 35 33 33 34 35 34 35 35 36 35 34 34 36 36 37 4 36 36 3737 38 38 38 39 39 38 40 41 41 38 41 5 38 36 37 34 37 37 36 37 37 37 3939 38 39 39 St Dev 1.6 1.9 2.2 1.8 1.2 1.6 1.3 1.7 1.1 1.9 2.6 2.6 2.11.5 2.0 Avg 36.0 36.0 36.6 35.8 37.0 36.8 36.8 37.6 37.4 37.8 38.6 38.438.4 38.4 40.0

FIG. 6 is a graphical representation of the averaged results of Tests Aand B in direct comparison. The y-axis shows the penetration force ingrams needed to pass a needle through the penetration membrane. Thex-axis shows the number of passes. The thick solid line represents theneedles that were dip coated with the base and top coating compositions,as set forth in Test A, while the thin solid line represents the needlesthat were swirl coated with the base and top coating compositions, asset forth in Test B.

As can be seen, the needles that were dip coated had an initialpenetration force of about 38 g. The penetration force increasedsteadily over the thirty passes, and the needles required an averagemaximum force of 61 g after thirty passes. In contrast, the needles thatwere swirl coated had an initial penetration force of about 31 g. Thepenetration force remained substantially constant over the thirtypasses, with the average maximum force after thirty passes being about40 g. As shown, the needles that were swirl coated required about 7 gless force in the beginning on average than the needles that were dipcoated, and the force remained substantially constant. Ultimately, theswirl coated needles required about 21 g less maximum force after thirtypasses than the dip coated needles.

Example 2

The penetration performance of various coating compositions and coatingmethods were also tested. In the following Tests A and B, two differenttypes of needle coating compositions and application methods wereexamined. The needles were passed through Monmouth rubber syntheticmedia.

Test A

In Test A, ten commercially available Ethicon BV-175 surgical needleshaving a 0.0078 inch diameter were tested. A coating was applied using adouble dipping procedure. In particular, a silicone dip was preparedusing a concentration of NuSil® Product No. MED4162 mixed with Micropro600 and Micromatte 2000 powders for lubrication as described above. Theneedles were placed on a moving carrier strip and dipped a first time.The needles were then flash cured in a hot box at approximately 225degrees Celsius for thirty seconds. The needles were then cured for 36hours in a convection oven at 163 degrees Celsius. The needles weredipped a second time, flash cured, and then cured in a convection ovenfor another 36 hours.

As shown in Table 3 below, ten needles were tested with thirty passesthrough the penetration membrane.

TABLE 3 Pass ---> Penetration [g] Experiment Needle 1 2 3 4 5 6 7 8 9 1011 12 13 14 15 A 1 35 38 37 38 38 38 38 39 38 38 40 40 41 42 41 2 35 3737 37 38 39 40 40 39 40 38 40 41 40 39 3 26 26 27 28 28 28 28 29 29 3031 31 31 30 34 4 28 29 31 32 32 32 32 33 33 33 34 34 34 33 34 5 28 34 3132 33 34 35 34 34 34 34 35 35 35 36 6 27 28 28 31 30 30 31 32 32 32 3434 35 32 34 7 34 35 36 37 38 37 38 38 38 39 39 40 40 39 41 8 27 34 32 3334 34 35 35 36 37 38 37 40 39 38 9 25 28 27 29 30 31 31 33 34 35 35 3637 37 36 10  25 27 29 30 29 31 31 30 31 31 31 32 32 33 34 St Dev 4.1 4.54.0 3.5 3.9 3.7 3.9 3.7 3.3 3.5 3.2 3.3 3.7 4.0 2.9 Avg 29.0 31.6 31.532.7 33.0 33.4 33.9 34.3 34.4 34.9 35.4 35.9 36.6 36.0 36.7 Pass --->Penetration [g] Experiment Needle 16 17 18 19 20 21 22 23 24 25 26 27 2829 30 A 1 40 40 42 43 42 40 42 42 43 42 44 43 41 40 43 2 44 39 43 39 4140 40 44 40 43 42 40 40 42 40 3 31 33 30 32 34 33 33 34 35 34 33 34 3534 35 4 36 35 36 37 38 37 36 35 36 38 38 38 38 38 38 5 36 35 36 38 37 3737 38 38 40 38 39 36 38 38 6 35 33 35 35 36 34 35 35 35 36 36 36 36 3636 7 41 41 40 40 40 41 41 42 42 40 42 42 45 41 41 8 39 41 40 39 40 40 4142 40 40 42 43 43 40 40 9 38 40 39 40 42 42 42 43 43 46 46 43 45 46 4610  34 33 34 33 34 33 34 34 34 35 34 34 36 36 34 St Dev 3.8 3.5 4.0 3.43.1 3.4 3.5 4.1 3.5 3.7 4.4 3.6 3.9 3.5 3.7 Avg 37.4 37.0 37.5 37.6 38.437.7 38.1 38.9 38.6 39.4 39.5 39.2 39.5 39.1 39.1

Test B

In Test B, ten Ethicon tungsten-rhenium alloy needles having an 0.008inch diameter were tested. The needles were prepared by applying theMomentive® SS4044P primer coat at room temperature. The primer coat wasflash cured at 200 degrees Celsius for 2-3 seconds. A base coatingcomposition was then applied over the primer using swirl coatingtechniques. The base coating composition was made by combining 27.58 wt.% of Momentive®, vinyl siloxane polymer, product no. MSC2631, with 72.25wt. % of the HFE 72-DE solvent and agitated for about five minutes.Momentive®, catalyst in toluene, product no. SS8010, was then added tothe mixture at 0.02 wt. %, and Momentive®, polymethyl hydrogen siloxane,product no. SS4300 was added at 0.14 wt. %. The base coating was appliedto the surgical needles using the Asymtek C-341 Conformal Coater and theAsymtek SC-300 Swirl Applicator. The needles were then heated to 300degrees Celsius for thirty seconds in an infrared heater.

A top coating composition was then applied to the needles and was formedfrom 26 wt. % of the NuSil® MED4162 silicone product combined with 74wt. % of the HFE 72-DE solvent. The top coating composition was alsoapplied using swirl coating techniques with the Asymtek C-341 ConformalCoater and the Asymtek SC-300 Swirl Applicator. The needles were againflash cured at a temperature of 190 degrees Celsius for approximatelythirty seconds.

The needles included in Test B were then batch cured at 80 degreesCelsius for three hours in a convection oven. The needles were tested bypassing each needle thirty times through the penetration membrane. Theforce required to do so is set forth in Table 4.

TABLE 4 Pass ---> Penetration [g] Experiment Needle 1 2 3 4 5 6 7 8 9 1011 12 13 14 15 B 1 22 22 22 23 23 22 22 23 21 23 23 22 22 22 22 2 22 2423 23 22 21 22 22 22 23 24 23 23 22 23 3 21 21 23 22 21 21 20 22 22 2122 21 21 22 22 4 21 21 22 22 24 23 24 24 25 23 23 24 24 24 24 5 21 21 2223 22 22 21 22 21 22 22 22 22 22 22 6 20 22 22 22 22 24 22 22 22 23 2322 22 22 23 7 21 23 22 22 21 22 22 23 22 23 21 23 22 22 22 8 21 23 22 2323 23 22 24 23 23 23 23 24 23 23 9 24 24 21 23 23 23 23 23 23 23 23 2324 25 24 10  21 21 21 20 20 21 21 20 21 21 22 21 21 22 21 St Dev 1.1 1.20.7 0.9 1.2 1.0 1.1 1.2 1.2 0.8 0.8 1.0 1.2 1.1 1.0 Avg 21.4 22.2 22.022.3 22.1 22.2 21.9 22.5 22.2 22.5 22.6 22.4 22.5 22.6 22.6 Pass --->Penetration [g] Experiment Needle 16 17 18 19 20 21 22 23 24 25 26 27 2829 30 B 1 21 22 23 23 23 22 24 22 22 23 22 23 23 24 23 2 23 24 23 24 2423 23 24 25 26 26 27 28 29 29 3 22 22 22 22 23 24 24 25 25 25 26 26 2628 28 4 26 25 24 24 24 24 25 26 25 25 25 26 26 25 26 5 22 22 23 23 23 2423 22 23 23 23 22 23 25 23 6 23 23 23 23 23 22 24 23 24 24 23 25 24 2424 7 23 22 23 23 23 24 23 23 23 25 24 23 25 25 24 8 22 23 23 24 24 24 2424 24 24 23 27 25 25 25 9 24 24 25 24 24 24 24 24 25 25 25 25 26 26 2610  22 22 21 22 22 22 22 22 23 22 23 23 24 24 23 St Dev 1.4 1.1 1.1 0.80.7 0.9 0.8 1.4 1.1 1.2 1.4 1.8 1.6 1.7 2.1 Avg 22.8 22.9 23.0 23.2 23.323.3 23.6 23.5 23.9 24.2 24.0 24.7 25.0 25.5 25.1

FIG. 7 is a graphical representation of the averaged results of Tests Aand B in direct comparison. The y-axis shows the penetration force ingrams needed to pass a needle through the penetration membrane. Thex-axis shows the number of passes. The thick solid line represents theneedles with conventional dip coating, as set forth in Test A, while thethin solid line represents the needles with the spray coating accordingto the present invention, as set forth in Test B.

As shown, the Test A needles initially required an average penetrationforce of about 29 g. The average penetration force for the Test Aneedles increased to 39 g after thirty passes. The Test B needles had aninitial average penetration force of 21 g and an average penetrationforce of 25 g after thirty passes.

Example 3

The following tests were performed to examine the effect coating methodshave on the force required to pass a needle through Monmouth rubbersynthetic media. The performance of needles that were dip coated wascompared with the performance of needles that were spray/swirl coated.

Test A

In Test A, four 0.026 inch diameter needles made from ETHALLOY® Alloyand having a taper cut point geometry were prepared for penetrationtesting. A base coating composition was prepared from a solution of 2.5g of Momentive®, vinyl siloxane polymer, product no. MSC2631, 22.15 g ofExxon Isopar-K, 0.0022 g of Momentive®, catalyst in toluene, product no.SS8010, and 0.0127 of Momentive®, polymethyl hydrogen siloxane, productno. SS4300. Four test needles were each dipped into the base coatingcomposition to coat their surfaces. The coated needles were then heatedto 200 degrees Celsius in a convection oven furnace for one hour.

A top coat coating composition was prepared using 2.50 g of NuSil®MED4162 with 22.50 g of Exxon Isopar-K. The four needles were then eachdipped into the top coating composition. The needles where then heatedto 140 degrees Celsius in a convection oven and cured for three hours.

Once cured, the four needles were each passed through the penetrationmembrane thirty times and the penetration force in grams was recorded asshown in Table 5 below.

TABLE 5 A Pass → Penetration (g) Needle 1 2 3 4 5 6 7 8 9 10 11 12 13 1415 16 1 61 71 78 84 88 95 97 101 100 104 108 110 110 109 110 111 2 65 6770 73 76 79 82 83 84 84 86 90 90 90 90 92 3 60 69 75 80 85 88 92 94 9598 99 100 102 102 103 101 4 62 65 69 73 76 79 82 84 86 88 89 92 92 94 9595 STDEV 2 3 4 5 6 8 8 9 8 9 10 9 9 8 9 8 AVG 62 68 73 78 81 85 88 91 9194 96 98 99 99 100 100 A Pass → Penetration (g) Needle 17 18 19 20 21 2223 24 25 26 27 28 29 30 1 111 112 110 112 114 112 113 113 112 116 114113 111 112 2 93 95 95 96 96 98 99 102 102 104 104 104 107 109 3 101 104107 104 103 104 104 103 105 107 107 105 108 108 4 95 97 124 121 122 125123 127 127 129 130 133 136 132 STDEV 8 8 12 11 12 12 11 12 11 11 12 1314 11 AVG 100 102 109 108 109 110 110 111 112 114 114 114 116 115

Test B

In Test B, five 0.026 inch diameter needles made from ETHALLOY® Alloyand having a taper cut point geometry were prepared for penetrationtesting. The needles were prepared by applying a base coatingcomposition using swirl coating techniques. The base coating compositionwas made by combining 27.58 wt. % of the Momentive®, vinyl siloxanepolymer, product no. MSC2631, with 72.25 wt. % of the HFE 72-DE solventand agitated for about five minutes. Momentive®, catalyst in toluene,product no. SS8010, was then added to the mixture at 0.02 wt. %, andMomentive®, polymethyl hydrogen siloxane, product no. SS4300 was addedat 0.14 wt. %. The base coating was applied to the surgical needlesusing the Asymtek C-341 Conformal Coater and the Asymtek SC-300 SwirlApplicator. The needles were then heated to 300 degrees Celsius forthirty seconds in an infrared heater.

A top coating composition was then applied to the needles and was formedfrom 26 wt. % of the NuSil® MED4162 silicone product combined with 74wt. % of the HFE 72-DE solvent. The top coating composition was alsoapplied using swirl coating techniques with the Asymtek C-341 ConformalCoater and the Asymtek SC-300 Swirl Applicator. The needles included inTest B were then batch cured at 140 degrees Celsius for three hours in aconvection oven.

Once cured, the five needles were each passed through a Monmouth rubbersynthetic media thirty times and the penetration force in grams wasrecorded as shown in Table 6 below.

TABLE 6 B Pass → Penetration (g) Needle 1 2 3 4 5 6 7 8 9 10 11 12 13 1415 1 66 69 70 70 71 70 70 72 70 70 72 71 72 72 74 2 58 60 60 61 61 61 6362 63 62 63 64 64 64 62 3 56 56 57 57 58 58 58 58 54 53 53 53 53 53 53 453 54 55 56 56 56 56 56 56 56 57 57 58 58 58 5 56 57 59 61 56 57 58 5958 59 60 60 60 59 57 STDEV 4.9 5.9 5.8 5.5 6.3 5.7 5.7 6.3 6.4 6.5 7.26.9 7.1 7.2 8.0 AVG 58 59 60 61 60 60 61 61 60 60 61 61 61 61 61 B Pass→ Penetration (g) Needle 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 174 75 76 76 76 76 76 76 75 76 74 75 74 73 73 2 64 66 65 66 67 68 68 6363 61 64 65 66 68 68 3 53 53 53 53 54 54 54 55 55 55 56 56 56 57 58 4 5858 58 58 58 60 60 59 60 60 60 60 61 61 61 5 59 59 60 60 61 60 61 61 6262 62 62 63 62 62 STDEV 8.0 8.5 8.7 8.8 8.6 8.5 8.4 7.9 7.4 7.9 6.7 7.26.7 6.3 6.0 AVG 62 62 62 63 63 64 64 63 63 63 63 64 64 64 64

FIG. 8 is a graphical representation of the averaged results of Tests Aand B in direct comparison. The y-axis shows the penetration force ingrams needed to pass a needle through the penetration membrane. Thex-axis shows the number of passes. The square points represent theneedles with the dip coating, as set forth in Test A, while the diamondpoints represent the needles with the spray coating according to thepresent invention, as set forth in Test B.

As shown, the Test A needles with the dip coating initially required anaverage penetration force of 62 g. The average penetration force for theTest A needles increased to 115 g after thirty passes. The Test Bneedles with the spray coating performed with an initial averagepenetration force of 58 g and resulted in an average penetration forceof 64 g after thirty passes. As can be seen, the needles in Test B withthe spray coating required significantly less penetration force up tothirty passes.

Example 4

The penetration performance of various coating compositions and coatingmethods were tested. In the following Tests A, B, and C, three differenttypes of needle coating compositions and application methods wereexamined. The penetration material for these tests was human cadavercarotid artery tissue.

Test A

In Test A, commercially available Ethicon BV-1 surgical needles having a0.0105 inch diameter were tested. A coating was applied using theprocedures associated with the manufacture of this series. Inparticular, a silicone dip was prepared using a concentration of NuSil®Product No. MED4162. The needles were placed on a moving carrier stripand dipped a first time. The needles were then flash cured in a hot boxat approximately 190 degrees Celsius for twenty seconds. The needleswere dipped a second time and flash cured again at the same settings asabove. Finally, the needles were dipped a third time and then cured in aconvection oven for 8 to 16 hours at 190 degrees Celsius.

Test B

In Test B, Ethicon tungsten-rhenium alloy needles having a 0.0105 inchdiameter were tested. The needles were prepared by applying theMomentive® SS4044P primer coat at room temperature. A base coatingcomposition was then applied over the primer using swirl coatingtechniques. The base coating composition was made by combining 27.58 wt.% of the Momentive®, vinyl siloxane polymer, product no. MSC2631, with72.25 wt. % of the HFE 72-DE solvent and agitated for about fiveminutes. Momentive®, catalyst in toluene, product no. SS8010, was thenadded to the mixture at 0.02 wt. %, and Momentive®, polymethyl hydrogensiloxane, product no. SS4300, was added at 0.14 wt. %. The base coatingwas applied to the surgical needles using the Asymtek C-341 ConformalCoater and the Asymtek SC-300 Swirl Applicator. The needles were thenheated to 300 degrees Celsius for thirty seconds in an infrared heater.

A top coating composition was then applied to the needles and was formedfrom 26 wt. % of the NuSil® MED4162 silicone product combined with 74wt. % of the HFE 72-DE solvent. The top coating composition was alsoapplied using swirl coating techniques with the Asymtek C-341 ConformalCoater and the Asymtek SC-300 Swirl Applicator.

The needles included in Test B were then batch cured at 80 degreesCelsius for three hours in a convection oven. The needles were tested bypassing each needle thirty times through the penetration membrane.

Test C

In Test C, a competing brand of commercially available surgical needles(0.010 inch diameter) was tested out of the package. The needles weretested by passing each needle thirty times through the penetrationmembrane.

FIG. 9 is a graphical representation of the averaged results of Tests A,B, and C in direct comparison. The y-axis shows the penetration force ingrams needed to pass a needle through human cadaver tissue. The x-axisshows the number of passes. The triangular points represent the needleswith the conventional dip coating, as set forth in Test A above. Thecircular points represent the needles prepared according to the presentinvention as forth in Test B above. The diamond points represent thecompeting brand of needles as set forth in Test C above.

As shown, the commercially available Test A needles having a dip coatinginitially required an average penetration force of about 16 g. Theaverage penetration force for the Test A needles increased to about 18 gafter thirty passes. The Test B needles with the coating according tothe present invention performed with an initial average penetrationforce of about 13 g and maintained this penetration force after thirtypasses. The competing brand of needles performed with an initial averagepenetration force of about 15 g and resulted in an average penetrationforce of about 25 g after thirty passes. As can be seen, the needles inTest B required significantly less penetration force up to thirtypasses.

The use of two coatings as described above with respect to the presentinvention results in surgical needles that exhibit reduced tissuepenetration force compared with standard surgical needles after anequivalent number of passes through tissue. Thus, both the lubricity ofthe needle as well as the durability of the coating is improved. This isbelieved to result for a number of reasons. For example, application ofthe base and top coats using a swirl coating process provides an evendistribution of the coatings over the substrate. Furthermore, thecomposition of the coatings in combination with the methods ofapplication and curing can result in significantly decreased averageforce required to repeatedly pass the needle through tissue. The curingtime is also significantly decreased, resulted in more efficientmanufacturing processes.

One skilled in the art will appreciate further features and advantagesof the invention based on the above-described embodiments. Accordingly,the invention is not to be limited by what has been particularly shownand described, except as indicated by the appended claims. Allpublications and references cited herein are expressly incorporatedherein by reference in their entirety.

What is claimed is:
 1. A method for coating a surgical needle,comprising: applying a primer coating to a surface of a surgical needleformed from a tungsten-rhenium alloy and having a tissue-penetrating endand a suture attachment end, wherein the primer coating comprisespolyalkylsiloxane and tetraethyl silicate, wherein the primer coating atleast partially covalently bonds with a surface of the surgical needlemade from the tungsten-rhenium alloy; applying a liquid base coatingthat differs from the primer coating to the primed surface of thesurgical needle; applying a top coating that differs from the basecoating onto the base coating, the base coating bonding with the topcoating; and curing the top coating to at least partially cross-link thetop coating.
 2. The method of claim 1, wherein the base coating enhancesthe durability of the top coating.
 3. The method of claim 1, wherein thebase and top coatings are spray-coated.
 4. The method of claim 1,further comprising, prior to applying the base coating and applying thetop coating, preparing the base coating from a mixture comprising avinyl functionalized organopolysiloxane and a hydrofluoroether solvent,and preparing the top coating from a mixture comprising apolydimethylsiloxane and a hydrofluoroether solvent.
 5. The method ofclaim 1, wherein applying the liquid base coating includes spraying theliquid base coating onto the primed surface of the surgical needle. 6.The method of claim 1, wherein the base and top coatings are appliedusing swirl coating.
 7. The method of claim 1, wherein a thickness ofthe top coating is at least about 50% less than a thickness of the basecoating.
 8. The method of claim 1, further comprising, after applyingthe base and top coatings and curing the top coating, treating thesurgical needle at a temperature in a range from about 80 degreesCelsius to about 165 degrees Celsius for a period of time in a rangefrom about three hours to about four hours.
 9. The method of claim 1,wherein each of the base and top coatings comprises a composition havinga solvent in an amount above 70% by weight.
 10. The method of claim 9,wherein the solvent comprises a hydrofluoroether solvent.
 11. The methodof claim 1, further comprising, prior to curing the top coating,subjecting the top coating to a temperature in the range from about 165degrees Celsius to about 200 degrees Celsius for a period of time ofless than about one minute.